1. Field of the Invention
The present invention generally involves the field of technology pertaining to fluid pumps. More specifically, the invention relates to an improved assembly for mounting the impeller of a fluid pump to the drive shaft of an electric motor in an automatic clothes washing machine.
2. Background of the Invention
A conventional automatic clothes washing machine is provided with a pump driven by an electric motor for directing fresh water into the clothes tub and removing spent water therefrom during a programmed sequence of washing, rinsing and spin drying cycles. The pump includes a rotary impeller contained within a housing having inlet and outlet ports. The impeller is directly driven by the drive shaft of the motor and an annular fluid seal is provided between the impeller housing and drive shaft to prevent leakage of water from the housing. The seal structure and manner in which the impeller is axially located with respect to the drive shaft comprise the basic features of an assembly for mounting the pump to the drive shaft. The configuration of this assembly affects the manufacturing cost, longevity and maintenance requirements of the pump.
It is known to directly attach the pump impeller to the drive shaft of the motor. This approach requires extending the hub of the impeller through the back of the pump and providing an appropriate means for attaching the hub to the drive shaft. In order to gain reasonable access to this attachment for maintenance purposes, the pump must be spaced a suitable distance from the motor, thus consuming additional axial space and requiring more material in forming the impeller housing and a longer drive shaft. A mounting assembly of this type also requires manipulation of the attachment between the impeller hub and drive shaft during installation and removal of the pump with respect to the motor.
It is also known to attach a pump impeller to a motor drive shaft by utilizing a bearing in the form of a "thrust button" for providing the end thrust required to axially locate the impeller on the drive shaft, with the thrust force being imposed by an appropriate clamp structure. A spring in the fluid seal of this assembly urges the impeller in a axial direction away from the drive shaft. This approach requires the additional cost of the thrust button.